Analysis of airfoil noise with an array of near- and far-field sensors
Abstract
Experimental techniques and analysis methods for characterizing the noise spectra of airfoils immersed in a subcritical Re flow in a wind tunnel are described. The multiple discrete frequencies are generated by aeroacoustic coupling on the airfoil. Flow disturbances which affect the sonic peaks can only be examined by sensors which do not themselves affect the flow. Detection in the near-field is achieved with microphones which identify the directivity of the emission. An antenna array of microphones is used in the far-field to pinpoint the source of the emissions, which are always pure tones in the far field. A proximity antenna for obtaining data on the directivity of both the pure tone peaks and the broadband emissions is presented. Autocorrelations are generated from data gathered at specific frequencies using the proximity array of microphones in the far field, and by decomposition of the field into plane waves in the near field.
- Publication:
-
Revue d'Acoustique
- Pub Date:
- 1982
- Bibcode:
- 1982RvAc...15..208G
- Keywords:
-
- Aerodynamic Noise;
- Airfoils;
- Noise Measurement;
- Directivity;
- Far Fields;
- Microphones;
- Near Fields;
- Noise Spectra;
- Acoustics